Description: A large and important family of herbs, shrubs, and soft-wooded trees, with a few lianas (Mendoncia). Acanthaceae have opposite leaves that are almost always toothed and usually anisophyllous (i.e., the two leaves in a pair are slightly different sizes). They lack stipules, but they have an interpetiolar ridge (a ridge of tissue running between the leaf bases) that can superficially resemble a stipule scar. The stems of Acanthaceae tend to be succulent and slightly swollen above the nodes, and may be ridged. Acanthaceae flowers are bilaterally symmetrical, with a fused 5-lobed corolla and four (sometimes two) stamens. The anthers join together in the center of the flower beneath the style. The flowers are often subtended by bracts, which may be the showier part of the inflorescence.

Economic uses: Many Acanthaceae are grown as ornamentals. Thunbergia is particularly popular here.